Phase-Field Study of Al Addition Effects on Dendritic Growth and Solute Segregation During Non-Isothermal Solidification of Mg-3wt%Y-1wt%Zn Alloy

A multi-component quantitative phase-field model was developed to investigate the influence of the Al addition on the solidification behavior of Mg-3wt%Y-1wt%Zn alloy. The study focused on the growth kinetics, solute segregation, and controlling mechanism of secondary dendrite arm spacing (SDAS) of α-Mg dendrites. The results show that Al addition significantly suppresses the growth rate of α-Mg dendrites and reduces the growth rate of solid fraction. Moreover, Al effectively mitigates Zn microsegregation, substantially decreasing the segregation ratio, while having only a minor effect on Y segregation. Furthermore, Al promotes SDAS refinement by lowering the liquidus temperature, inhibiting solute diffusion, and reducing solid/liquid interfacial energy. Constitutional undercooling analysis indicates that higher Al content enhances solute accumulation, leading to increased undercooling, thereby altering dendritic nucleation and growth. This study provides valuable insights for optimizing the solidification microstructure and enhancing the mechanical properties and corrosion resistance of Mg-Y-Zn-Al alloys.